In civil aviation, outlet ports for aircraft sewage are designated as a drain-mast. The drain-mast is located beneath the aircraft fuselage and releases so-called greywater into the atmosphere, which generally comprises the condensate of the cargo spaces and the outer doors, as well as the washwater of all of the hand wash basins and accordingly, has contaminants (such as soap, for example) as well as colored contaminants, such as kitchen waste, like coffee, tea, or juices. The underside of the aircraft fuselage therefore may be soiled with the removal of the greywater into the atmosphere by these contaminants, whereby the function of flaps, valves and the like may be impaired. Because of these contaminants, the underside of the fuselage should either be cleaned or at least be monitored for possible contaminants.
DE 103 01 374, for example, discloses connecting the discharge port of the drain-mast via a bellows to the aircraft-internal grey water system. This connection, however, is complicated, since the mounting of the drain-mast must be done blind, that is, without an unobstructed view on the individual components, since the bellows is concealed in a recess behind the outer skin of the fuselage. In the worst case, therefore, the bellows may bend or snap off during mounting of the drain-mast, which can lead to a sealing of the connection, without this error being noticed immediately. As a result, a complete stoppage of the greywater system during the flight could occur. As a result of the badly accessible and deformable motor bellows design, therefore, a quick and simple exchange of a damaged drain-mast (for example as a result of stoppage, defective heating elements, mechanical damage) frequently is not possible. The design of the drain-mast described in DE 103 01 374 may be disadvantageous, because a separate ground wire must be installed for lightning protection, and a pressure range limit between the housing of the drain-mast and the cabin area in which the air leakage rate of the aircraft and also the energy consumption of the climate control unit increases, is not permitted.